Foundation construction

ABSTRACT

A plurality of precast ground bearing foundation pads are provided at spaced-apart locations. Precast wall sections span between and bear upon the pads, each pad having a groove in its upper surface for receiving and holding a base of the wall section. Separate foundation holes may be excavated for each pad, the holes are backfilled to fix the pads in position.

RELATED APPLICATIONS

[0001] This application claims the benefit of the New Zealand patentapplication No. 511899 filed May 23, 2001.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to the prefabrication offoundations, and more particularly, but not by way of limitation, toprefabricated foundations to support residential and commercialbuildings.

[0004] 2. Description of the Related Art

[0005] In typical current construction practice, foundations forbuildings are formed by excavating a foundation hole, assembling formswithin the hole to effectively form a mould, pouring concrete within theassembled forms, and then removing the forms when the concrete has set.The foundation is then left standing in the foundation hole, which isbackfilled around the exterior of the foundation. The remainder of thebuilding is then constructed atop the poured foundation. As a result ofthis process, construction progress is highly dependent on the timelycompletion of the foundation. This can lead to difficulties in areaswhere soil conditions delay or hinder the digging of the foundationhole, and where the climate is not agreeable to pouring of concrete,owing to rain in particular.

[0006] Further difficulties with properly forming a foundation areinherent in the pouring process. Because foundation walls must be pouredwithin vertically-oriented forms, the concrete mix must have a low“slump” value, that is it has to be sufficiently fluid to fill out allcomers, prevent voids, etc. However, in order for the concrete mix toreach this low slump value a substantial amount of water must be used inthe concrete mix. This results in weaker, lower-density concrete, withgreater permeability to water after setting occurs. Further, a wateryconcrete mix results in longer concrete setting/curing times. Thisfurther slows building construction because backfilling against anewly-poured foundation before it slows building construction becausebackfilling against a newly-poured foundation before it is fully set maycause the foundation walls to collapse, or may crack them to later allowwater to enter the foundation. Other drawbacks associated withfoundations poured on sire include the difficulty in obtaining a goodquality exposed surface due to poor workmanship in constructing theform. Ensuring correct placement of reinforcing steel, particularly togive the correct concrete cover, is also problematic

[0007] Precast concrete foundations walls have been proposed to overcomesome of the problems associated with cast in situ foundations walls. Themanufacture of precast wall panels in a factory avoids the problemsassociated onsite quality control and the vagaries of the weather. Oncea crushed gravel base for the precast sections is in place, the precastsystem can be erected very quickly. The problem associated with thismethod of construction however is the accuracy required in forming thebase of crushed metal. Due to the narrow bearing area along the base ofthe wall, a considerably depth of crushed aggregate has to be provided.Precise preparation of the crushed metal is required in order to supportthe precast walls upon a flat and true surface for the full length ofthe foundations.

[0008] U.S. Pat. No. 4,125,980 describes a foundation which includescast insitu concrete footings provided at spaced apart locations aroundthe perimeter of the building to be erected. Precast reinforced concretebeams are set in place with each beam bearing on adjacent footings. Tojoin the beams and to fasten them to the footing adjacent ends of eachbeam are formed with a keyway and a concrete column is poured whichextends through this keyway and hardens to secure the beams in place.The disadvantage of this method of constructions is it still relies uponconcrete which is poured on site and which is vulnerable to weather,seasonal and climate limitations and the general human errors and lackof precision associated with this type of construction.

SUMMARY OF THE INVENTION

[0009] It is an object of the present invention to address the foregoingproblems or at least to provide the public with a useful choice. Furtheraspects and advantages of the present invention will become apparentfrom the ensuing description which is given by way of example only.

[0010] According to one aspect of the present invention there isprovided a foundation assembly, including at least two precast groundbearing foundation pads at spaced-apart locations, and at least oneprecast wall section spanning between and bearing upon said pads,wherein each pad has means for receiving a base of said wall section.

[0011] The foundation assembly may form part of a building construction,a retaining wall or a fence or the like. Henceforth reference will bemade to building construction, however this should not be seen aslimiting and the variations described will apply equally to other likeconstructions.

[0012] Preferably each precast wall and pad includes a cast sectionwhich is formed of concrete or other cementitious materials.Alternatively other materials such as composite materials may beemployed.

[0013] In a building construction the wall sections extend generallyvertically from the pads, above the ground level and preferably up toapproximately the floor level. Alternatively, the walls may extend tointegrally form the sides of a building. The walls include surfacesadapted to support wall or floor structures, including brick and blockwalls, and timber framed walls and floors.

[0014] Preferably adjacent wall sections are abutted. Abutting faces maybe shaped for inter-engagement. At joints between wall sections asealant or adhesive may be applied, or an intermediate sealing elementmay be provided.

[0015] One or more intermediate foundation pads may be provided betweentwo pads spanned by a wall section. All corners in a wall section a repreferably supported by a pad.

[0016] Preferably each said pad is laterally fixed by fill materialsurrounding the sides of the pad. The fill material is self-compactinggranular material, crushed metal, other aggregate or concrete compactedaround the sides of the pad.

[0017] Preferably the said means for holding the base of the wallincludes at least one groove into which the base is received. Preferablythe groove has parallel vertical faces adapted to engage correspondingvertical faces of the wall. The groove may be lined with a channelmember cast into the top of the pad. The groove is aligned with thelongitudinal axis of the wall, thereby acting to fix the base laterally.

[0018] Optionally other means of holding the base to the wall may beprovided, including brackets and fasteners of a known type. Optionallythe means for holding the base of the wall may include means forperforming small adjustments of the position of the wall 40 relative tothe pad 1.

[0019] Preferably each said wall section is laterally fixed by fillmaterial on either side of the wall section.

[0020] Preferably adjacent wall sections abut to form a substantiallycontinuous ring foundation. The ring foundation may surroundsubstantially the whole of a building or alternatively only apartthereof.

[0021] Preferably the said wall sections are topped by a cast in situconcrete floor slab. Alternatively the said wall sections support afloor of joist type construction, prefabricated construction or otherconstruction.

[0022] Optionally, the wall sections may include reinforcing elementsprojecting from one or more faces thereof. These reinforcing elementsmay include a helical wire coil or substantially straight rods.

[0023] The inside faces of adjacent wall sections may be joined by anangle bracket fixed to fasteners cast into the said inner faces.Alternatively, the upper faces of adjacent wall sections may be joinedby a bracket having a slot for adjusting the joint opening.

[0024] Preferably the pad includes a pad fixture and the wall includes awall fixture, the pad fixture and wall fixture being adapted forengagement with a lever for manual manipulation of the position of thewall relative to the pad. Most preferably, the pad fixture is a V-shapedpad recess formed in an upper surface of the pad in a medial section ofthe groove. Most preferably, the wall fixture is a wall recess in thevertical face of the wall, having a pair of opposed walls elongated inthe vertical direction.

[0025] A cast in situ foundation strip may extend between two adjacentpads. The strip may be cast into permanent or temporary formwork ordirectly into the open excavated trench.

[0026] A pad may alternatively be supported upon and fixed to a pilefooting. Preferably the pad is fixed to the pile by an adhesive, such asgrout. Preferably, the pad includes an aperture having a shoulder forabutment against an end of the pile footing and a smaller sectionopening into the base of the groove adapted for the injection ofadhesive therethrough.

[0027] According to another aspect of the present invention there isprovided a method of constructing a foundation assembly substantially asdescribed above, the method including the steps:

[0028] a) lining the base of a pad excavation with a bed ofself-compacting granular material;

[0029] b) placing one pad on the bed of compacted material;

[0030] c) surrounding the pad with fill material to set it in position,and

[0031] d) placing the wall section upon the pad.

[0032] Alternatively the base of a pad excavation may be lined withcrushed aggregate compacted in situ or optionally with concrete. Themethod may be repeated for each pad in a construction.

[0033] Preferably the sites of the pad excavations are deeper than anyexcavation therebetween.

[0034] According to another aspect of the present invention there isprovided a method substantially as described above including the furthersubsequent step:

[0035] e) surrounding the sides of the said wall section with fillmaterial.

[0036] According to another aspect of the present invention there isprovided a precast concrete foundation pad with a substantially planarground bearing base, sides, and a groove extending the full width of atop of the pad, the groove having substantially vertical sides adaptedto receive and hold a precast wall section.

[0037] The size of the pads and the number of the pads is chosen inaccordance with a known manner depending upon the bearing strength ofthe soil. The sides may be tapered or straight. Alternatively a pad mayhave three or more sides, or may be circular or oval or the like.

[0038] One preferred embodiment of the pad has a rectangular outline inplan view and the top includes two grooves of the same depth, thelongitudinal axes of which intersect at right angles.

[0039] This invention provides a prefabricated foundation system whichis effective and versatile in operational use, and allows foundations tobe constructed more quickly than has previously been possible. Thelength of time during which foundation excavations are open andtherefore vulnerable to the weather is greatly reduced, with significanttime savings for building construction. This invention satisfies a need,particularly in low cost housing, for a durable concrete foundationcapable of being erected by taking advantage of the economy of precastunits and also having an inexpensive system for assembling the precastunits into a completed structure. The components themselves may beeconomically constructed and have an overall simple design whichminimizes manufacturing costs and maximizes performance.

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Further aspects of the present invention will become apparentfrom the following description which is given by way of example only andwith reference to the accompanying drawings in which:

[0041]FIG. 1 is a pictorial view of a foundation assembly of the presentinvention;

[0042]FIGS. 2a and 2 b are details of a joint of FIG. 1;

[0043]FIG. 3 is a pictorial view of a join between two wall sections ofa foundation assembly of the present invention;

[0044]FIGS. 4a-4 d illustrate four sequential stages in the constructionof the foundation assembly of FIG. 1;

[0045]FIGS. 5a-5 f are sectional elevations of a foundation assembly ofthe present invention adapted for different floor and wallconstructions;

[0046]FIGS. 6a-6 f are pictorial views of five different embodiments ofa foundation pad of the present invention;

[0047]FIG. 7 is a pictorial view a part of a wall and a pad of thepresent invention;

[0048]FIG. 8 is a plan view of a continuous ring foundation of abuilding employing the foundation assembly of the present invention;

[0049]FIG. 9 is a pictorial view of a foundation assembly of the presentinvention showing a tapered wall section, and

[0050]FIG. 10 is a plan view of a continuous ring foundationincorporating two different wall elements;

[0051]FIG. 11 is a pictorial view of a foundation system of the presentinvention including a cast in situ strip footing;

[0052]FIG. 12 is a pictorial view a part of a wall and a pad of thepresent invention fixed to a pile foundation;

[0053]FIG. 13 is a sectional view through the pad of FIG. 12; and

[0054]FIG. 14a and 14 b are pictorial views of the intersection ofmultiple walls in a foundation assembly of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0055] Referring to FIG. 1 of the drawings, a foundation assembly of thepresent invention includes two spaced apart foundation pads 1 a, 1 b.The designations 1 a, 1 b etc. refer to different embodiments of ageneral foundation pad 1 according to the present invention (a likemethod of designation is also used in referring to other componentsdescribed herein). The foundation pads 1 are formed from precastreinforced concrete and include a generally planar ground engaging base2, sides 4 and a top 3.

[0056] Spanning between the foundation pads 1 a, 1 b is a precastconcrete wall section 40 a having substantially parallel vertical sides41, 42 and upper and lower edges 43 and 44 respectively.

[0057] Formed in the top 3 of each foundation pad 1 are grooves 30 forreceiving and holding the wall section 40, the bottom edge 44 of whichbears upon the foundation pads 1. Two walls 40 a, 40 b intersect atapproximately right angles and are supported upon a comer pad 1 b. Abevel joint 45 (shown in detail in FIG. 2) is provided at theintersection.

[0058] Referring to FIG. 2a, the bevel joint 45 includes an anglebracket 47 on the internal faces 42 between the walls 40 a, 40 b. Theangle bracket 47 is fastened to the walls 40 a, 40 b by means of cast infasteners 48. A seal 46 is provided for water proofing the joint 45.Although formed in modular sections the present foundation assembly canactually provide greater resistance to water entry than “single-piece”poured foundations. Poured foundations are highly susceptible tocracking somewhere along their lengths, whereas the walls 40 of thepresent invention are smaller and less susceptible to stress cracking.Further, the walls 40 will alleviate stress by flexing at the joints 45between abutting modules. Provided these joints 45 have beenwaterproofed by means of a sealant/adhesive, water is unlikely to enter.

[0059]FIG. 2b illustrates an alternative square butt joint detail wherethe fastenings connecting the wall sections are only fixed temporarilyduring construction and which have the advantage of being reusable. Theupper edges of the wall sections 40 a, 40 b are joined at the joint by abracket fixed by fasteners 48, 48′. One end of the bracket 147 isslotted to provide adjustment for opening and closing the joint.Preferably the fasteners 48, 48′ are bolts which engage with femalethreaded inserts (not shown) molded into the upper edges of the wallsections 40 a, 40 b.

[0060]FIG. 3 illustrates additional brackets 47 and tie strips 49 whichmay be employed for connecting the walls 40 and for fastening the walls40 to the pads 1. Due to the tongue- and-groove type connection betweenthe walls 40 and pads 1, the brackets 47 connecting them provideresistance to longitudinal (with respect to the longitudinal axis of thewall) or uplift loads due to wind or earthquake.

[0061] The method of constructing the foundation assembly of the presentinvention is illustrated. with reference to FIG. 4a to 4 d. FIG. 4aillustrates an excavation 54 for the installation of a comer typefoundation pad 1 b. The excavation 54 for the foundation pad is made toa depth 51 below the surrounding ground level 50. The excavation 55 isprovided between pad excavations 54 to accommodate the base of the wall(not shown) and need only be of a lower depth 53. Next the base of theexcavation 54 is lined with a bed of self-compacting granular material59 which is carefully levelled.

[0062] Next the foundation pad 1 b is placed upon the bed of compactedmaterial 59 (FIG. 4b) and it is then surrounded by compacted fillmaterial 57 to set it in position. (FIG. 4c). The wall sections 40 a, 40b are then placed upon the foundation pad 1 b e.g. by a crane. Shims(not shown) may be used to provide any adjustment required in theposition of the walls 40. Any gap in the connection between the pads 1and the wall 40 may be filled with grouting, cement or similar loadbearing filler. Referring to FIG. 4d, once the walls 40 a, 40 b havebeen finally positioned and the brackets 47 or fastener strips 49 arefixed, backfill 58 may be placed on either side of the wall 40 a, 40 band compacted ensuring that material is placed beneath the bottom edge44 to provide some intermediate support for the wall 40.

[0063] The walls 40 may include varying constructional details dependingupon the proposed building constructions. A selection of details fordifferent walls 40, 140, 240, 340, 440, 540 are illustrated in FIGS.5a-5 f. The wall section 40 (FIG. 5a) includes a steel reinforcing rod60 which protrudes from an upper part of the inner wall 64. The wall 40supports a cast insitu floor slab 63 and has a recessed edge 61 providedalong with front face 62 of the wall 40 to support brick cladding 65.

[0064] The wall section 140 (illustrated in FIG. 5b) includes a recessededge 68 which locates the cast insitu floor slab 63. FIG. 5c illustratesa wall section 240, which like wall section 140 includes a horizontalstarter rod 60, but has an additional starter rod 69 to extend insidethe lower blocks 70 of a concrete masonry block wall. FIG. 5dillustrates a wall section 340 adapted for use with a timber flooringsystem having a recess 71 adapted to support a timber stringer 72. FIGS.5e and 5 f show walls 440 and 540 respectively without recessed edgesfor locating the floor slab 63. Wall 440 (FIG. 5e) is reinforced withsteel wire mesh 73 and to key into the slab 60 a helical coil of steelreinforcing wire 74 is cast into the inner face of the wall. Openings(not shown) may be provided in the walls 40 for services, ventilationetc.

[0065] In a typical pad 1, two walls 40 will be joined. FIG. 6aillustrates a comer pad 1 b for joining two walls (not shown) at rightangles. The L shaped groove 30 in the top 3 has vertical sides 73supporting each of the wall sections 40.

[0066]FIG. 6d illustrates a pad 1 a having a straight groove 30 whichcan be used either for joining two walls 40 or at an intermediateposition between the ends of a wall 40. FIG. 6c shows a pad 1 c havingan angle shaped groove 30. FIG. 6b and 6 e illustrate pads 1 d and 1 ehaving a T shaped groove 30 and cross shaped grooves 30 respectively. Inthe pads 1 a-1 e the grooves 30 extend medially across the upper face 3.FIG. 6f illustrates a groove 30 formed closer to an edge 4 of the pad 1f, in order to allow the wall 40 to be positioned close to a boundaryline 74, for example, without the pad 1 f encroaching beyond theboundary.

[0067] Another feature of the pads and the walls is illustrated in FIG.7, which shows the means by which the wall 40 may be manipulated duringconstruction relative to the pad 1 b. The drawing illustrates a comerpad 1 b having V-section recesses 91 formed in the upper face 3 thereof,the recesses being adapted to engage with a lever 93 which is alsoprovided with lugs 94 for engagement with recesses 92 formed in thevertical face of the wall 40. In the preferred embodiment illustrated,the pad recesses 91 are formed in a medial section of each of the twoperpendicular sections of the groove 30 having their axis generallyperpendicular to the axis of the adjacent groove section. The padrecesses 91 are shaped to engage with a pointed tip 95 of the lever 93.The wall recess 92 has a pair of opposed walls elongated in the verticaldirection and has a depth to accommodate the length of the lugs 94. Itwill be appreciated that the recesses 91 and 92 may be positioned sothat the corresponding edge of the pad 1 or wall 40 may be engaged withthe lever 93. For example, the wall recess 92 could be located directlyabove the edge of the pad 1 b, allowing the lever 93 to gain purchaseagainst the side of the footing pad 1.

[0068] As illustrated in FIG. 8, in constructing a foundation for abuilding 100, foundation pads 1 are provided at each corner of thebuilding 100. In the preferred embodiment this ring beam foundation istopped by a cast insitu concrete floor slab 63 which assists in tyingtogether the separate wall elements 40.

[0069] It will be appreciated by those skilled in the art that manydifferent variations of the shape and dimensions of both the walls 40and the pads 1 are contemplated by the present invention. Illustrativeof some of these variations are a tapered wall 40 (FIG. 9) to accountfor a sloped contour on the ground. Although the walls are generallypanel shaped, optionally, ribbing (not shown) may also be included.

[0070]FIG. 10 illustrates the construction of a simple building such asa garage, workshop or the like. The corner details X and Y refer to thehelical coil reinforcement and horizontal starter rod arrangements shownin FIGS. 5e and 5 f respectively, which may or may not be combined in asingle structure such as this. In lightweight buildings a single pad 1at each corner of the foundation is sufficient, depending upon thebearing strength of the soil. The modular nature of these buildingsallows the wall and roof construction to be started as soon as thefoundations are erected, and before backfilling or floor slabinstallation. In this case this foundation system offers a furtheradvantage of allowing the floor slab to be poured in a substantiallyenclosed space, letting construction to proceed without delay caused byinclement weather.

[0071]FIG. 11 illustrates the use of the present foundation system in amanner allowing it to be adapted to accommodate either poor groundconditions or higher loadings by providing a continuous strip footing.The ground is prepared to receive a concrete strip cast in situ betweenthe two foundation pads 1 which supports the intermediate part of thewall 40. The wall 40 is positioned and held in the pads 1, formwork 80is run on either side between the pads 1 with reinforcing 60 placed asis desired, before pouring the intermediate section. Optionally theperimeter of a building may be completed in this manner.

[0072]FIGS. 12 and 13 illustrate an alternative to the above-describedmethod to accommodate either poor ground conditions or higher loadings.In this embodiment a pile footing 101 is provided to support thefoundation walls 40, with a pad 1 connected therebetween. Preferably anadhesive, such as grout is used to fix the pad 1 to the top of the pile101, once it has been located.

[0073] In the embodiment illustrated in FIG. 13, the pad 1 includes anaperture having a shoulder 75 for abutment against the end of the pile101 and a smaller section 76 opening into the base of the groove 30.Before placing the wall section 40, grout may be injected into theaperture to fasten the pad 1 and the pile 101.

[0074]FIGS. 14a and 14 b show the manner in which intersections betweenwalls 40 may be accommodated by different pads 1d, 1e. The walls 40 willgenerally have the same thickness as a standard concrete foundationwall, e.g., 150-300 mm, and may be configured to have any desired heightand length. The wall 40 dimensions may vary widely to suit theparticular application. It is expected that in most applications,adjacent walls 40 will have the same height and width, but variations inlength between different walls 40 will be relatively common.

[0075] Aspects of the present invention have been described by way ofexample only and it should be appreciated that modifications andadditions may be made thereto without departing from the scope thereof.

What is claimed is:
 1. A foundation assembly, including: at least twoprecast ground bearing foundation pads at spaced-apart locations, and atleast one precast wall section spanning between and bearing upon saidpads, wherein each pad has means for receiving a base of said wallsection.
 2. The foundation assembly of claim 1 wherein said means forreceiving the base of the wall includes at least one groove into whichthe base is received.
 3. The foundation assembly of claim 2 wherein saidbase has vertical sides and said at least one groove has correspondingvertical sides.
 4. The foundation assembly of claim 1 wherein adjacentwall sections are abutted with a seal provided therebetween.
 5. Thefoundation assembly of claim 1 wherein each said pad is laterally fixedby fill material surrounding the sides of the pad.
 6. The foundationassembly of claim 1 wherein each said wall section is laterally fixed byfill material on either side of the wall section.
 7. The foundationassembly of claim 1 wherein adjacent wall sections abut to form asubstantially continuous ring foundation.
 8. The foundation assembly ofclaim 1 wherein said wall sections are topped by a cast in situ concretefloor slab.
 9. The foundation assembly of claim 1 wherein the said wallsections include surfaces adapted to support wall or floor structures.10. The foundation assembly of claim 1 wherein the said wall sectionsinclude reinforcing elements projecting from one or more faces thereof.11. The foundation assembly of claim 1 wherein the said pad includes apad fixture and the wall includes a wall fixture, the pad fixture andwall fixture being adapted for engagement with a lever for manualmanipulation of the position of the wall relative to the pad.
 12. Thefoundation assembly of claim 11 wherein the pad fixture is a pad recessformed in an upper surface of the pad and the wall fixture is a wallrecess in the vertical face of the wall.
 13. The foundation assembly ofclaim 12 wherein the pad recess is V-shaped in section and is formedadjacent to a medial section of the groove.
 14. The foundation assemblyof claim 12 wherein the wall recess has a pair of opposed wallselongated in the vertical direction.
 15. The foundation assembly ofclaim 1 further including a cast in situ foundation strip extendingbetween two adjacent pads and supporting the intermediate section of thewall.
 16. The foundation assembly of claim 2 wherein a pad is supportedupon and fixed to a pile footing.
 17. The foundation assembly of claim16 wherein the pad includes an aperture having a shoulder for abutmentagainst an end of the pile footing and a smaller section opening intothe base of the groove adapted for the injection of adhesivetherethrough.
 18. The foundation assembly of claim 1 wherein insidefaces of adjacent wall sections are joined by an angle bracket fixed tofasteners cast into the said inner faces.
 19. The foundation assembly ofclaim 1 wherein upper faces of adjacent wall sections are joined by abracket having a slot for adjusting the joint opening.
 20. A method ofconstructing a foundation assembly, including: at least two precastground bearing foundation pads at spaced-apart locations, and at leastone precast wall section spanning between and bearing upon said pads,wherein each pad has means for receiving a base of said wall section,the method including the steps: lining the base of a pad excavation witha bed of self-compacting granular material; placing one pad on the bedof compacted material; surrounding the pad with fill material to set itin position; and placing the wall section upon the pad.
 21. The methodof constructing a foundation assembly of claim 20 wherein the sites ofthe pad excavations are deeper than any excavation therebetween.
 22. Themethod of constructing a foundation assembly of claim 20 including thefurther subsequent step: surrounding the sides of the said wall sectionwith fill material.
 23. A precast concrete foundation pad with asubstantially planar ground bearing base, sides, and at least one groovein a top of the pad, the groove having substantially vertical sidesadapted to receive and hold a precast wall section.
 24. A precastconcrete foundation pad as claimed in claim 23 including a pad fixtureadapted for engagement with a lever for manual manipulation of theposition of the wall relative to the pad.